In the methods and system of this disclosure, a computer based cardiac mapping/EP tools system is disclosed along with the methodology for monitoring esophageal temperature, as well as, a fluoroscopy (or medical images) based mapping for Cryoballoon ablation (or Pulmonary vein isolation PVI). The system may also be used for radiofrequency (RF) atrial fibrillation ablations. The general methodology for the system is described in conjunction with the flow diagram in FIG. 1A for cryoballoon ablations and FIG. 1B for radiofrequency ablations.
For cryoballoon ablations, as shown in conjunction with FIG. 1A, at the beginning of the procedure (step 450), the patient is connected to the fluoroscopy based mapping step 452. Also, an esophageal probe is placed at the appropriate level of the esophagus for measuring esophageal temperature (steps 454 & 456) and connected to the mapping system 458.
In the setup of the Mapping System 458, fluoroscopy and/or medical images (e.g. intracardiac echo or ICE) are acquired into the mapping system (step 464), as well as, patient's electrical signals (both intracardiac and surface EKG) as shown in step 460. Esophageal temperature is also acquired into the Mapping System 458, and temperature based alarms and/or automatic shutoff is programmed in the computer at the beginning of the case, based on change from the baseline temperature.
The role of the mapping system is to help place the cryoballoon catheter in the appropriate location with the left atrium and pulmonary veins. To this end, high resolution images are recorded in the system with contrast medium (“dye”) injections. The recordings may be done manually by the operator who manually starts and stop the recordings, or may be done in an automatic fashion utilizing optical character recognition (OCR) as a switch, described later in this disclosure.
Once the detailed images of the pulmonary veins are recorded, (step 466) the live fluoroscopy images are superimposed on the “enhanced” images of the pulmonary veins (obtained with “dye” injections), as shown in step 468 and described later in this application. Once the two images are superimposed, a transparency factor between the live image and recorded image is adjusted (step 470) to guide the physician in placing the cryoballoon in the appropriate position, step 472. Once the cryoballon is placed appropriately, freezing or cryoablation is started at physician's orders.
Advantageously, in this procedure the system not only guides in the optimal visual placement of the cryoballoon, but also monitors the esophageal temperature, and the system acts to activate alarms and/or cut-off the ablation energy delivery based on pre-determined criteria as was set in step 462.
As well known in the art, atrial fibrillation ablations may be performed utilizing radiofrequency (RF) ablation or cryoablations. The system described in this disclosure may be used for RF or cryoablations. The flowchart in FIG. 1B describes similar steps for RF ablations. These are steps 480 from beginning of procedure to step 508 to the end of the procedure. Even though the methodology for sequence of events is similar, radiofrequency ablations is generally a much more lengthier procedure as the ablation lesions are performed point by point via a much smaller catheter, typically also containing means for contact force sensing.